Mercury contact interrupter



Feb. 8, 1938. 5 UB 2,107,742

MERCURY CONTACT INTERRUPTER Filed Jan. 25, 1935 I INVENTOR I Samael 1901/ ATTORNEY Patented Feb. 8, 1938 PATENT OFFICE 2,101,742 MERCURY CONTACT m'rmmur'rra Samuel Ruben, New Rochelle, N. Y.

Application January 25, 1935, Serial No. 3,372

14 Claims.

This invention relates to interrupters and more particularly to devices for producing periodic interruptions in electric currents.

An object of the invention is the provision of an interrupter device which is adapted, when connected in an electric current circuit, to cause periodic variations or interruptions in the current flowing therein. Such a device, in combination with a suitable electrical circuit, may be used to produce pulsating direct current or the circuit may be arranged to provide alternating current, or to raise or lower the potential of electrical energy supplied by a current source.

A further object of the invention is to improve the means for supplying electric potentials to radio apparatus and particularly to automobile radio receivers where it may be used for supplying high direct current potentials, such as B bias potentials, thereto.

Another object is to improve the means for supplying electric potentials and currents to special types of electrical equipment, such as special ray tubes, gas discharge devices, inert gas tubes, neon signs, signal devices and the like.

Other objects of the invention will be apparentfrom the following description and accompanying drawing taken in connection withthe appended claims.

The invention maybe embodied in a cell member comprising a chamber in which a bath of mercury, or mercury amalgam is in contact with a high resistance surface, such as the surface of any of certain materials having a high contact resistance. Such a surface may be provided; for example, by a cadmium oxide element or by one made of magnetic oxide 'of iron, boron carhides, certain forms of tungsten, tungsten carbide, vanadium pentoxide, various types of carbon, graphite, carbon compounds adapted to have a high contact resistance with mercury and which do not appreciably react therewith, and the like. For producing the current interruptions the cell may be connected in a circuit including a potential source for applying a potential difference across the surface between the mercury element and the resistance element.

The invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture referred to above or which will be further" brought out' and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawing, the scope of'the invention being indicated in the appended claims.

For a fuller understanding of the nature and objects of the inventions as well as for specific fulfillment thereof, reference should be had to the following detailed description taken .in connection with the accompanying drawing, in which;

Figure 1 is a top view of an interrupter cell embodying the present invention;

Figure 2 is a section on line 2-4 of Figure 1;

Figure 3 shows the cell and a circuit therefor adapted to supply a direct current potential; and

Figure 4 shows a cell embodied in a tube structure.

Like reference characters indicate like parts in the several figures of the drawing.

While a-preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the construction of parts without departing from the spirit of the invention. 4 5

Referring to the drawing, and particularly to Figures 1 and 2 the cell 9 comprises a hollow tubular conductive shell l0, formed of a con-v ductive metal such as steel. Shell i0 is provided with a concentric hole or bore ll of a first diameter from its .upper end to a mid-portion thereof and of a larger diameter from said mid-' portion to the lower endof the shell. The hole H is tapped at its upper, small-diameter end to receive a sealing screw I2 and the shell I0 is threaded externally at its lower end to provide attachment for a cap [3 having an opening H at its center.

Fitted snugly within'the large diameter portion of hole II. is a ring l5 of insulating material, such as lavite, for example, the inside surface thereof being formed into a tapered portion. Against this tapered portion is'fitted the cone shaped end of a rod l6.

Rod I6 is composed of a material adapted to form a high resistance contacting surface with mercury or mercury amalgam. "Cadmium oxide is preferred for this purpose. Other materials having high contact resistance, such as forms of carbon, graphite, magnetic oxide of iron, carbon hexaboride, tungsten,tunsgten carbide, other,

pentoxide can.

oxide may be mixed with a. dilute water glass solution (such as a 5% aqueous solution of sodium silicate) to form a thick plastic mass which may then be molded into rod shape and then sintered. .Cadmium oxide is preferred for the contacting rod l6 for a number of reasons,

-among which may be mentioned the high stawhich it comes in contact.

A threaded bolt i1 is molded into the rod l6 and extends out of the lower end of the cell through opening 14 in cap l3. Rod I6 and its integral bolt I! are insulated from cap l3 by an insulating washer I8, which may be made of mica, for example. It will be noted that rod 16 is insulated from the rest of the cell structure by insulating members I5 and I8 and is provided with an electrical connecting terminal by bolt II. It is also apparent that the cone-shaped end of rod it closes the lower end of a chamber 19 formed in shell in by the small-bore portion of hole II and the sealing screw 12 and that the area of the rod l6 exposed within the chamber is determined by the size of the hole in insulating ring l5.

The chamber I9 is partly filled with mercury 20 containing another metal, such as silver, amalgamated therewith in order to reduce its resistance. The preferred proportions of mercury and silver is about 100 parts mercury to 1 part silver by weight. Other amalgams may be used in place of silver amalgam, such as those containing gold or copper or combinations of these metals. Silver is to be preferred, howeven'because of its low resistance and high chemical stability. It reduces the chemical activity of the mercury at high temperatures and increases the contact resistance. In any instance the added metals are not sufiicient to reduce the amalgam to a solid state as it is desired that the bath remain liquid within the chamber. A contacting surface 31 is accordingly formed between the mercury 20 and the resistance material of rod l6.

Means for connecting electrical conductors are provided on the outside of the cell, nut 36 on sealing screw l2 providing one terminal connection and nuts 2i on bolt ll providing the other terminal connection.

The operation of cell 9 is as follows: If a direct current potential of 6 to 8 volts, for example, is applied across the two terminals of the cell electric current will pass through the cell from the upper terminal through sealing screw [2, metal shell l0, mercury bath 20, contacting surface 31, rod i6 and bolt H to the lower terminal. While there is no outward visible appearance of any activity within the cell it will be found by connecting a suitable indicating instrument, such as a telephone receiver, for example, in the external circuit that the current passing through the cell is being interrupted at a frequency of several hundred cycles per second, the frequency depending upon the proportions of the cell and the composition of the parts. This pulsating current is produced irrespective of the polarity of the direct current connections.

It is believed that the current interruptions or variations are produced at the contacting surface 31 between the mercury and the resistance material. This is indicated by the fact that certain materials having as high or higher specific volume resistance than the materials listed do not produce interruptions unless a very high current is passed, at which time, only slow irregular interruptions occur. It is further indicated by the fact that the energy expended in the device appears to be dissipated from surface 31.

It is thought that the heat generated by the passage of current through the relatively highresistance surface is sufficient to cause a layer of gas or mercury vapor to form over the surface thereby stopping the current. As soon as the current is stopped, however, the heat becomes dispersed through the surrounding material allowing the gas or vapor to condense or become re-absorbed thereby again closing the circuit and allowing current flow. This cycle appears to be repeated several hundred times a second thereby producing the above mentioned pulsating current.

There is no apparent sparking or arcing at the surface and if such occurred the elements are well protected from deterioration since the column of mercury shuts out all air and other gases from the contact surface.

The device appears to be very stable and constant in operation changing very little with continued operation or with changes in temperature. The interruptions begin as soon as the external circuit is closed and continue with constant amplitude and frequency as long as potential is supplied to the terminals. While the cell may become considerably heated during operation due to the expenditure of energy therein this appears to have very little effect upon the interruptions.

Figure 3 shows the interrupter cell 9 connected in a circuit for supplying a high direct voltage, such as may be used as B potential for automobile radio receivers and the like. Cell 9 is supplied with direct current from a low-voltage source such as battery 22 one terminal of which is connected by conductor 23 with the lower terminal of the interrupter cell. The other terminal of battery 22 is connected by conductor 24 to one side of primary winding 25 of a set-up transformer. The other side of primary winding 25 is connected by conductor 26 with the upper terminal of the interrupter cell.

Condenser 2'! is connected across the interrupter cell terminals to absorb the inductive voltage of transformer primary 25 when the circuit is broken by the interrupter. This condenser, in practice, has been made of 4 microfarads capacity but other values can be used, of course, if desired.

The ends of high-voltage secondary winding 28 of the transformer are connected to two similar terminals of .full-wave rectifier device 30 of a well-known and standard design. A small buffer condenser 28 (of 0.1 microfarad, for example) is connected acro'ss the terminals of secondary winding 28. The center tap of winding 28 is connected through filter circuit 3| to one of the high voltage output terminals 40 adapted to In the operation of the circuit shown in Figure 3 the battery 22 applies a low D. C. potential across the terminals of interrupter 8 which periodically interrupts the current in the above described manner. The interrupted direct current thus produced flows through primary winding 25 of the step-up transformer inducing a high-potential alternating current in the secondary 28. The output of secondary 28 is rectified by full-wave rectifier 30 and fluctuations are smoothed out by filter 3| so that asubstantially constant high D. C. potential is applied across output terminals 40.

While it is not necessary in most cases to en- 'close cell 9 in any sort of protective insulation or shielding it may occasionally be advantageous to do so. In Figure 4 cell 9 is shown enclosed in a sealed glass envelope 32 and the two terminals of the cell are connected through base 33 with prongs 34 and. 35, respectively. The envelope 32 may be evacuated or may be filled with an inert gas such as argon, neon or the like, or one of the cooling gases helium or hydrogen may be used to aid in heat dissipation. Envelope 32, instead of being glass, may-be of metal to further aid in heat dispersion.

Interrupters which have been used heretofore for B potential circuits and other uses have generally been of the electromagnetic vibratory reed type. They are disadvantageous, however, in that the wear on the contacts varies with varying output characteristics and they are both mechanically and electrically noisy due to their structure and to the character of circuit interruptions'they produce.

The present invention eliminates all of these difliculties. There are no wearing parts requiring adjustment or replacement, mechanical noise is unnoticeable and the character of the interruptions produced are such as to produce verylittle electrical noise in the output. Likewise a wider range of frequencies can be produced by varying the dimensions and composition of the parts. While 200 to 300 cycles is generally preferred it is possible to attain frequenciesmany times higher, if desired.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of theappended claims.

What is claimed is:

1. An electric current interrupter adapted to produce autonomic periodic current 'interruptions and comprising a bath of mercury and a contacting element having a surface in contact with said mercury bath, said contacting element being formed of a material capable of providing a high-resistance surface between itself and said mercury bath. V

2. An electric current interrupter adapted to produce autonomic periodic current interruptions and comprising a bath of mercury and acontacting element having a surface in contact with said mercury bath, said contacting element being formed of a material selected from the group consisting of cadmium oxide, carbon, magnetic oxide of iron, boron carbides, tungsten, tungsten carbide, vanadium pentoxide, and carbon compounds adapted to have a high contact resistance with mercury and which do not appreciably react therewith, said material being characterized by the ability to form a high-resistance contacting surface with mercury.

3. An electric current interrupter comprising a bath of mercury and a cadmium oxide contacting element in contact with said mercury bath, said interrupter being adapted to produce autonomic periodic interruptions. in an electric current.

4. An electric current interrupter cell adapted to produce periodic interruptionsin an electric current independent of any external periodic control and comprising an element having a contacting surface. and a column of mercury in contact with and standing above said surface, said surface being of relatively high resistance.

5. An electric current interrupter cell adapted to produce autonomous periodic interruptions in an electric current and comprising a first terminal, a solid element electrically connected thereto, a second terminal, a mercury bath electrically connected thereto, said solid element and said mercury bath having a high resistance contacting surface therebetween.

6. An electric current interrupter adapted to produce autonomic periodic current interruptions and comprising a bath of mercury amalgam and a contacting element having a surface in contact with said mercury amalgam bath, said contacting element being formed of a material capable of providing a high-resistance surface between itself and said mercury amalgam bath.

7. An electric current interrupter adapted to produce autonomic periodic current interruptions and comprising a bath of mercury-silver amalgam and a contacting element having a surface in contact with said mercury-silver amalgam bath, said contacting element being formed of a material selected from the group consisting of cadmium oxide, carbon, magnetic oxide of iron,

boron carbides, tungsten, tungsten carbide, vanadium pntoxide, and carbon compounds adapted to have a high contact resistance with mercury and which do not appreciably react therewith, said material being characterized by the ability to form a high-resistance contacting surface with mercury-silver amalgam.

8. An electric current interrupter comprising a bath of mercury amalgam and a cadmium oxide contacting element in contact with said mercury for electric currents comprising a mercury bath.

and an electrode of resistance material in contact therewith.

12. A mercury interrupter comprising a mercury bath and an electrode in contact therewith of such nature that electric current may be passed across the contact surface and will result in an increase in the resistance between said contact surfaces to a high value without perceptibq separating said surfaces and without changing the area over which said surfaces are in contiguous relation.

13. An electric current interrupter adapted to produce autonomic periodic current interruptions and comprising a bath of nircury and a contacting element being formed of a material capable of providing a high-resistance surface ,between itself andsaid mercury bath, said devicebeing adapted to cause autonomic interruptions without appreciably shifting the bath of mercury.

14. An electric current interrupter cell adapted to produce periodic interruptions in an electric current independent of any external periodic control and comprising an element having a contacting surface and a column of mercury in contact with and standing above said surface and having its entire contacting surface at substantially the same depth in said mercury column.

SAMUEL RUBEN. 

